High Dose monthly Vitamin D supplements don’t seem protective against cancer, a JAMA Oncology study reports. Previous studies have found an inverse relationship between serum vitamin D levels and cancer risk, but supplementation hasn’t produced consistent results.
Researchers used data from a New Zealand study examining the effect of high-dose supplements on cardiovascular health. In their post hoc analysis they used national cancer registries to compare cancer incidence and mortality in roughly 5000 participants randomized to vitamin D (200,000 IU oral bolus plus monthly 100,000 IU) or placebo. Participants ranged in age from 50 to 84 and were recruited from Auckland family practices.
During their median 3.3-year participation, cancer incidence was almost identical in the two groups: 6.5% with vitamin D and 6.4% with placebo.
The authors wondered whether daily or weekly doses — or a longer duration of supplementation — would bring different results.